This invention relates to an assembly and a method for fastening a stent onto a catheter. This kind of device finds routine use in the area of percutaneous transluminal coronary angioplasty (PTCA) procedures, although it may be used in other types of procedures, as well.
Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Inflation expandable stents are well known and widely available in a variety of designs and configurations. Inflation expandable stents are crimped to their reduced diameter about the delivery catheter, then maneuvered to the deployment site and expanded to the vessel diameter by fluid inflation of a balloon positioned between the stent and the delivery catheter. The present invention is particularly concerned with the crimping of inflation expandable stents although self-expanding stent may be crimped as well.
An example of a stent is described in PCT Application NO. 960 3092 A1, published Feb. 8, 1996, the content of which is incorporated herein by reference.
In advancing a stent through a body vessel to a deployment site, the stent must be able to securely maintain its axial position on the delivery catheter, without translocating proximally or distally, and especially without becoming separated from the catheter. Stents that are not properly secured or retained to the catheter may slip and either be lost or be deployed in the wrong location or partially deployed. In securing a stent to a catheter, however, the stent must be crimped in such a way as to minimize or prevent altogether distortion of the stent and to thereby prevent abrasion and/or reduce trauma of the vessel walls.
In the past, crimping has been done by hand often resulting in the application of undesired uneven forces to the stent. Such a stent must either be discarded or re-crimped. Stents which have been crimped multiple times can suffer from fatigue and may be scored or otherwise marked which can cause thrombosis. A poorly crimped stent can also damage the underlying balloon.
Recently, stent crimping devices have been disclosed in U.S. Pat. No. 5,546,646 to Williams et al, U.S. Pat. No. 5,183,085 to Timmermans et al., U.S. Pat. No. 5,626,604 to Cottone, Jr., U.S. Pat. No. 5,725,519, to Penner et al., U.S. Pat. No. 5,810,873 to Morales, WO 97/20593 and WO 98/19633.
All U.S. patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
In order to properly crimp a stent in accordance with the present invention it would be desirable to produce a device, optionally portable, to crimp a stent onto a catheter uniformly while minimizing the distortion of and scoring and marking of the stent and due to the crimping. This may be accomplished in the present invention, in its many embodiments, by applying an inward force to a stent mounted upon a catheter using a loop of reducible diameter.
The present invention is therefore directed to a stent crimper comprising a crimping member disposed in a reducible diameter loop with at least one pulling member extending from the loop. A stent and optionally catheter are placed in the loop and the diameter of the loop reduced by pulling on the pulling member thereby crimping the stent, optionally to the catheter.
Stent crimpers based on the loop construction may comprise a plurality of such crimping members. Desirably, a sleeve will be present between the crimping member and the stent to protect the stent and/or spread the crimping force more uniformly over the stent. Each crimping member has at least one member.
The invention also relates to methods of crimping a stent to a catheter using a loop based stent crimper. Generally, a stent disposed about a catheter is inserted into the one or more loops of the stent crimping device. The diameter of the loop is then reduced by pulling on one or more of the loop ends thereby crimping the stent to the catheter.